Streptomyces hygroscopicus subsp. hygroscopicus 5-4: A Potential Biological Control Agent for Fusarium Wilt of Banana

The microorganism that inhibits Foc TR4 is endophytic actinomycetes, originating from various tissues of medicinal plants. These microorganisms include Nonomuraea, Kitasatospora, and Streptomyces. Among them, strain 5-4 isolated from the roots of Piper austrosinense exhibits broad-spectrum antifungal activity, producing chitinase and β-1,3-glucanase. It is identified as Streptomyces hygroscopicus subsp. hygroscopicus 5-4. This strain significantly reduces the disease index of banana wilt. Furthermore, exogenous application of strain 5-4 increases the expression levels of defense genes such as phenylalanine ammonia-lyase (PAL), peroxidase (POD), pathogenesis-related protein 1 (PR-1), hydrolytic enzymes (β-1,3-glucanase), lysin motif receptor kinase 1 (LYK-1), and mitogen-activated protein kinase 1 (MPK-1). The antifungal mechanism assay demonstrates that extracts of strain 5-4 inhibit spore germination and hyphal growth of Foc TR4, causing abnormally swollen, deformed, and ruptured hyphae of Foc TR4. Therefore, S. hygroscopicus subsp. hygroscopicus 5-4 could be used as a potential biological agent for controlling Fusarium wilt of banana.